I was just going by the documentation but maybe its not necessary 
https://zwave-js.github.io/zwavejs2mqtt/#/usage/custom-device-files
After looking around online, I found out there is a version 2 of the module (I had a version 1). The version 2 is Z-Wave Plus where the version 1 is just Z-Wave. While this wouldn’t make a difference, it is possible the version 1 info has been removed. Either way, I got a version 2 module in, remove the old, installed the new, and now it ID’s correctly.
Probably never added.
Maybe submit this info as GitHub issue on zwavejs so they know to add it and that it work